1. Field of the Invention
The present invention relates to wheelchair lifts or elevators and, more particularly, to combination stair and folding platform wheelchair lifts which translate from one configuration to the other depending upon the purpose to be served. Still more particularly, the present invention relates to an improved operating design and actuating mechanism for such a lift.
2. Description of the Prior Art
The art of combination folding stair and platform wheelchair lifts, which translate from one configuration to the other depending upon the purpose to be served, is well-developed.
A relatively early example which illustrates the presently generally accepted concept of wheelchair lifts like the present invention is disclosed in U.S. patent Ser. No. 4,027,807 for a Wheelchair Lift, issued Jun. 7, 1977, to Graham R. Thorley. Thereshown is an elevator or lift for a wheelchair, or physically impaired person, which is particularly adapted to replace the entrance/exit stairs of a public transportation vehicle such as a bus, trolley, or light rail train car. The Thorley '807 patent discloses a set of stairs having step and riser panels which transform into a horizontal lift platform to operate as an elevator. The outer or end panel of the platform in some designs serves both as a ramp at the end of the platform and as a safety barrier, when it flips upward from the end of the platform, to prevent a wheelchair from rolling off the end thereof during vertical motion of the platform. An improved design for such a barrier is disclosed in applicants' related application.
Wheelchair lifts are presently made in the convertible stair/platform configuration for a specific purpose which is to be installed or retrofitted into the door system of a large multi-passenger vehicle to permit wheelchair users to have access to public transportation as mandated by federal regulations. The wheelchair lift collapses into a stair configuration within the door system of a vehicle to permit use by frilly mobile persons. However, once the doors are open, the stair configuration can be transformed first into a platform by collapsing the stair panels into a horizontal array which projects outward from the bus so that it extends beyond the side thereof for a sufficient distance to extend over a curb. The stairs, upon flattening, are typically disposed, in the prior art designs, at bus floor level which permits a wheelchair-bound or physically-impaired person inside the bus to roll or step onto the platform and then be lowered to the ground. Alternatively, upon extension, the platform can be lowered either to ground or curb level to permit a wheelchair or physically impaired person to be rolled or step thereon and then lifted to bus floor level for movement into the bus. The bus driver/wheelchair lift operator thereafter transforms the lift back into a stair configuration and the doors are closed.
Once the platform has been raised to bus floor level and the wheelchair moved into the bus, the rift operator selects the step configuration control. The barrier/ramp panel then usually retracts inward around the outboard end of the platform to lie flat on top of the outer panel of the platform during the transformation of the lift from platform to stair configuration at which time the barrier/ramp then serves the function as the tread of the bottom step of the stair configuration of the wheelchair lift.
These designs of the prior art include many operating problems because of the complex mechanisms and procedural operations required to sequentially convert the elevator between the stairs and platform configurations. More importantly, some have specific deficiencies which are capable of causing injury to passengers when there is a malfunction or when they are operated incorrectly. The present invention overcomes these problems and provides new and improved operating methods and actuating mechanisms for transforming the combination folding stair and platform wheelchair lifts between the two configurations and for operation of the lift in the elevator functioning mode.